Caking of nitrogen-containing materials consisting essentially of ammonium salts useful as an ingredient of fertilizer poses a serious problem in the art. Caking makes it difficult to handle the materials in bulk form at the factory and also significantly interferes with the application of the fertilizer by the final user. Thus, for example, bagged fertilizer which has been compressed requires additional handling in order to be put into commercially acceptable form.
This caking may be caused by, for example, the formation of crystalline bridges according to which solid connections are formed at the points of contact among the granules. Alternatively, there may be capillary adhesion or bonding between the granules with a significant force often being necessary to break this adhesion or bonding. Naturally, the cohesive forces will vary based on storage conditions and other variables; however, in all cases the caking presents a serious problem which has long sought effective solution.
Several methods have been proposed to overcome this problem which generally involve the use of additives to the fertilizer composition. Typical additives include the use of finely divided powders which must cover the fertilizer substantially uniformly such as for example talc, kaolin and diatomaceous earth. Alternatively, surfactants are frequently used such as non-ionic surfactants, as the polyoxylenes, the anionic surfactants, for example, the alkyl-aryl-sulfonates and in particular the sulfonates derived from benzene and naphthalene. Alternatively, cationic surfactants have been used, especially the amines derived from long chain fatty acids. These additives form a hydrophobic film around the fertilizer granules and simultaneously reduce the surface tension of the intergranular solution, lower the angle of contact and thereby exert a beneficial effect on the caking problem. Further additives include compounds that also tend to form a hydrophobic film around the fertilizer granules such as paraffin wax, polyolefin wax and mineral oils. However, it has been found that compositions used heretofore are not entirely effective in eliminating the caking problem. Moreover, many of these additives are not desirable in the fertilizer composition, others tend to be expensive and require relatively large amounts thereof.
Accordingly, it is a principal object of the present invention to provide an anti-caking composition that flows freely and resists caking even on prolonged storage.
It is a further object of the present invention to provide an anti-caking composition as aforesaid for use with a nitrogen-containing material consisting essentially of ammonium salts useful as an ingredient of fertilizer and normally posing a problem with caking, especially ammonium sulfate.
It is a still further object of the present invention to provide an anti-caking composition as aforesaid which utilizes a relatively inexpensive additive in relatively small amounts and which is easy and economical to use on a commercial scale.
Further objects and advantages of the present invention will appear hereinbelow.